Benchmark for comparing stackalloc to heap allocations for small, medium, and large arrays.

stackalloc-benchmark.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace StackAllocVsHeapAlloc
{
    public static class Sandbox
    {
        private const int ITERATIONS = 10000;
        private const int REPETITIONS = 5;
        
        public static int ArraySize = 86000;

        private static void Measure(string what, Action action)
        {
            action(); // warm up
            
            double[] results = new double[REPETITIONS];
            for (int i = 0; i < REPETITIONS; ++i)
            {
                Stopwatch sw = Stopwatch.StartNew();
                action();
                results[i] = sw.Elapsed.TotalMilliseconds;
            }
            Console.WriteLine("{0} - AVG = {1}, MIN = {2}, MAX = {3}",
                what, results.Average(), results.Min(), results.Max());
        }

        public static void Go()
        {
            Console.WriteLine("Array size: " + ArraySize);

            Measure("Heap Array ", () =>
            {
                for (int i = 0; i < ITERATIONS; ++i)
                {
                    GetSquare(i % ArraySize);
                }
            });

            Measure("Stack Array", () =>
            {
                for (int i = 0; i < ITERATIONS; ++i)
                {
                    GetSquareStack(i % ArraySize);
                }
            });
        }

        public static int GetSquare(int value)
        {
            int[] someNumbers = new int[ArraySize];
            for (int i = 0; i < someNumbers.Length; ++i)
            {
                someNumbers[i] = value;
            }

            return someNumbers[value];
        }

        public unsafe static int GetSquareStack(int value)
        {
            int* someNumbers = stackalloc int[ArraySize];
            for (int i = 0; i < ArraySize; ++i)
            {
                someNumbers[i] = value;
            }

            return someNumbers[value];
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 10; i < 5000; i += 500)
            {
                Sandbox.ArraySize = i;
                Sandbox.Go();
            }
            for (int i = 6000; i < 100000; i += 10000)
            {
                Sandbox.ArraySize = i;
                Sandbox.Go();
            }
        }
    }
}